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Message-ID: <20240108171506.k47t4qztbbhulsp3@quack3> Date: Mon, 8 Jan 2024 18:15:06 +0100 From: Jan Kara <jack@...e.cz> To: Fengnan Chang <changfengnan@...edance.com> Cc: tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org Subject: Re: [PATCH v6] ext4: improve trim efficiency On Fri 01-09-23 17:28:20, Fengnan Chang wrote: > In commit a015434480dc("ext4: send parallel discards on commit > completions"), issue all discard commands in parallel make all > bios could merged into one request, so lowlevel drive can issue > multi segments in one time which is more efficiency, but commit > 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex") > seems broke this way, let's fix it. > > In my test: > 1. create 10 normal files, each file size is 10G. > 2. deallocate file, punch a 16k holes every 32k. > 3. trim all fs. > the time of fstrim fs reduce from 6.7s to 1.3s. > > Signed-off-by: Fengnan Chang <changfengnan@...edance.com> This seems to have fallen through the cracks... I'm sorry for that. > static int ext4_try_to_trim_range(struct super_block *sb, > struct ext4_buddy *e4b, ext4_grpblk_t start, > ext4_grpblk_t max, ext4_grpblk_t minblocks) > __acquires(ext4_group_lock_ptr(sb, e4b->bd_group)) > __releases(ext4_group_lock_ptr(sb, e4b->bd_group)) > { > - ext4_grpblk_t next, count, free_count; > + ext4_grpblk_t next, count, free_count, bak; > void *bitmap; > + struct ext4_free_data *entry = NULL, *fd, *nfd; > + struct list_head discard_data_list; > + struct bio *discard_bio = NULL; > + struct blk_plug plug; > + ext4_group_t group = e4b->bd_group; > + struct ext4_free_extent ex; > + bool noalloc = false; > + int ret = 0; > + > + INIT_LIST_HEAD(&discard_data_list); > > bitmap = e4b->bd_bitmap; > start = max(e4b->bd_info->bb_first_free, start); > count = 0; > free_count = 0; > > + blk_start_plug(&plug); > while (start <= max) { > start = mb_find_next_zero_bit(bitmap, max + 1, start); > if (start > max) > break; > + bak = start; > next = mb_find_next_bit(bitmap, max + 1, start); > - > if ((next - start) >= minblocks) { > - int ret = ext4_trim_extent(sb, start, next - start, e4b); > + /* when only one segment, there is no need to alloc entry */ > + noalloc = (free_count == 0) && (next >= max); Is the single extent case really worth the complications to save one allocation? I don't think it is but maybe I'm missing something. Otherwise the patch looks good to me! Honza > > - if (ret && ret != -EOPNOTSUPP) > + trace_ext4_trim_extent(sb, group, start, next - start); > + ex.fe_start = start; > + ex.fe_group = group; > + ex.fe_len = next - start; > + /* > + * Mark blocks used, so no one can reuse them while > + * being trimmed. > + */ > + mb_mark_used(e4b, &ex); > + ext4_unlock_group(sb, group); > + ret = ext4_issue_discard(sb, group, start, next - start, &discard_bio); > + if (!noalloc) { > + entry = kmem_cache_alloc(ext4_free_data_cachep, > + GFP_NOFS|__GFP_NOFAIL); > + entry->efd_start_cluster = start; > + entry->efd_count = next - start; > + list_add_tail(&entry->efd_list, &discard_data_list); > + } > + ext4_lock_group(sb, group); > + if (ret < 0) > break; > count += next - start; > } > @@ -6959,6 +6950,22 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group)) > break; > } > > + if (discard_bio) { > + ext4_unlock_group(sb, e4b->bd_group); > + submit_bio_wait(discard_bio); > + bio_put(discard_bio); > + ext4_lock_group(sb, e4b->bd_group); > + } > + blk_finish_plug(&plug); > + > + if (noalloc && free_count) > + mb_free_blocks(NULL, e4b, bak, free_count); > + > + list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) { > + mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count); > + kmem_cache_free(ext4_free_data_cachep, fd); > + } > + > return count; > } > > -- > 2.20.1 > -- Jan Kara <jack@...e.com> SUSE Labs, CR
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